Infrared light sources including semiconductor light-emitting diodes and semiconductor lasers are useful for many applications including fluoride-based optical-fiber communications, spectroscopy, chemical and pollution sensing, process monitoring, and infrared laser radar and countermeasures. However, the performance of infrared light sources in the 2-6 .mu.m wavelength range has been limited by nonradiative recombination processes (usually Auger recombination) which dominate radiative recombination in narrow-bandgap semiconductors.
Infrared lasers termed "quantum cascade" lasers have recently been disclosed by Capasso et al in U.S. Pat. Nos. 5,457,709; 5,509,025 and 5,570,386. Such "quantum cascade" lasers are based on intersubband transitions of electrons in a multilayer semiconductor structure that comprises doped semiconductor material of only a first conductivity type. Such "quantum cascade" lasers are not based on electron-hole recombination, and do not include a semimetal region.
An advantage of the infrared light source of the present invention is the provision of a semimetal region within the active region to produce electrons therein for the generation of infrared light.
Another advantage of the present invention is that a plurality of active regions can be stacked to form an infrared light source that emits at a plurality of different wavelengths, or to form an infrared light source having a broadband emission.
A further advantage is that the infrared light source of the present invention can be formed as a light-emitting diode (LED) or as a laser.
Yet another advantage of the present invention is that a laser structure can be formed with a plurality of vertically stacked active regions to provide an increased gain and lasing output power.
These and other advantages of the infrared light source of the present invention will become evident to those skilled in the art.